Various constructions of welding sleeves made from a thermoplastic material are known in which the ends of the thermoplastic line elements, i.e. pipe sections, shaped members, terminations and other fittings are interconnected. It is common to all these constructions that the adjacent surfaces of the line elements and the welded sleeve are in part melted and joined with the aid of a heating conductor in which electrical heat is produced.
The production of electrical welding sleeves is relatively complicated, because it is largely dependent thereon whether a satisfactory connection of the ends of the line elements is obtained or not. Welding sleeves in which a coil of an electrical resistance heating wire is arranged in the vicinity of the inner wall of a sleeve member has proved very satisfactory. However, it must be ensured that on the one hand an interturn short-circuit of the resistance heating wire is reliably avoided, a layer of turns in the immediate vicinity of the inner wall is ensured and that on the other hand a reliable connection with the contact points for connecting the electrical welding sleeve to a supply unit is obtained. Although it is possible to fulfil these requirements, manufacture partly takes place by manual operations.